P1398 Glow Plug Circuit Low Voltage Bank 2
The P1398 code indicates that the Powertrain Control Module (PCM) has detected an abnormally low voltage signal in the glow plug control/monitoring circuit for Bank 2. In diesel engines such as the Power Stroke 6.0L, 6.4L, and 6.7L, this means the circuit is not drawing the expected current or the voltage feedback is below the calibrated threshold, preventing effective preheating of the cylinders in that bank.
01. Most Common Causes
02. Symptoms You Will Notice
- Hard starting, especially in cold weather
- White smoke from exhaust on startup
- Check Engine Light illuminated
- Rough idle or misfire until engine warms up
03. Step-by-Step Diagnosis
Scan for additional codes and check freeze frame data
Visually inspect glow plug fuses and replace if blown
Test glow plug resistance on Bank 2; replace any open or out-of-spec plugs
Check voltage and ground at the glow plug connector with key on
Inspect wiring and connectors for damage, corrosion, or loose connections
Test the Glow Plug Control Module (GPCM) output to Bank 2
If all else passes, consider PCM reprogramming or replacement
1. Frequently Asked Questions
Is it safe to drive?▼
You can drive short distances in mild weather, but starting will be difficult in cold conditions and continued driving may cause excessive smoke and potential engine damage. It's best to repair promptly.
How much does it cost to fix?▼
Repair costs typically range from $200 to $800, depending on the cause. Glow plug replacement is $200-$400, a GPCM can be $300-$600, and wiring repairs vary.